The present invention relates generally to printed-wiring board mounted onto electronic devices, such as personal computers (hereinafter referred to as xe2x80x9cPCsxe2x80x9d), and more particularly to a method for identifying the printed-wiring board. The printed-wiring board to which the present invention is applicable covers a broad range of printed-wiring boards, such as those to be mounted onto a PC, a cellular phone and other electronic devices.
Along with the recent technology development, electronic devices, such as PCs and cellular phones, have become increasingly smaller and adopted more diversified designs. Accordingly, a wide variety of shapes of circuit boards have also been used from motherboards to be mounted onto PCs and cellular phones to package circuits (sometimes referred to as a Chip Sized Packages (xe2x80x9cCSPsxe2x80x9d). These printed-wiring boards (referred to as a xe2x80x9cboardxe2x80x9d hereinafter unless otherwise specified) include a conductive part, such as a wiring pattern, and the conductive part includes a plurality of fine pads which assist in an electric connection between terminals of a circuit element, such as a semiconductor chip, and the wiring pattern.
Some manufactures produce such printed-wiring boards by themselves, while others are supplied with these printed-wiring boards from one or more vendors. Generally, in requesting a third party to manufacture the above printed-wiring boards, a PC manufacturer, for example, provides its vendor with a schematic blueprint of the board as manufacturing data readable with a CAD/CAM, and requests the vendor to deliver the boards. In response, the vendor processes and modifies the manufacturing data such that the vendor may actually produce the board, and then submits the modified data to the manufacturer for permission, after putting down ID data (referred to as an xe2x80x9cidentifierxe2x80x9d hereinafter), such as an alphanumeric character, onto an insulating part on the board.
The identifier is usually expressed, for example, through etched and cutout letters in a conductive layer closest to the board surface, a marking process using ink onto the board surface, and a stamp process. Any of these methods may visualize the identifier for microscopic test.
However, as the recent reduced board size and wiring high-density progress, it often becomes difficult to indicate the identifier on the board. For example, in a CSP as a typical example, the reduced board size and wiring high-density narrow a space for the identifier made of marked, stamped, and etched or cutout letters. On the other hand, even when there is a space enough for the identifier, some PC manufacturers often refuse the insertion of the identifier to keep board""s external appearance. For example, a certain PC manufacturer uses some vendors, and prefers the same external appearances for all the boards delivered from these vendors; for this reason, the PC manufacturer does not like to allow these vendors to indicate their unique identifiers.
The PC manufacturer performs an acceptance test for boards delivered from the vendor, and returns to them those boards which have been determined as inferior products. The vendor then attempts to investigate the cause and state of any returned, inferior board, but could not if the board does not have any identifier that enables the vendor to find out board""s manufacture date, shipping date, type, etc. Therefore, there has been a demand to provide a board with an identifier.
As an identification approach without greatly marring board""s external appearance, Japanese Laid-Open Patent Application No. 6-296065 proposes putting an identifier onto board""s disused board part located around and cut down from a product part that is used as a finished product. Nevertheless, the method according to this reference cannot neither identify the product part that has been separated from the disused board part, nor investigate the inferior products. Japanese Laid-Open Patent Application No. 6-112603, on the other hand, proposes identifying a board by forming a plurality holes in the insulating part instead of using alphanumerical characters, and by opening and closing each of them. However, it is still unlikely to obtain permission from a manufacturer since this reference uses the same approach as the prior art in forming an identifier in board""s non-conductive portion, and it expensively requires a special machine to form and read these holes.
Accordingly, it is an exemplified object of the present invention to provide a method for identifying a printed-wiring board without marring board""s external appearance, a printed-wiring board treated by this identifying method, and a method for manufacturing such a printed-wiring board.
In order to achieve the above objects, a printed-wiring board of one aspect according to the present invention to be mounted with a circuit element includes a plurality of pads which assist in an electric connection between the circuit element and a wiring pattern, at least one of the plurality of pads being used to serve as an identifier for identifying the printed-wiring board. This printed-wiring board uses pads originally provided to the printed-wiring board to identify the printed-wiring board. In addition, it may identify the product part since it is mounted with the circuit element, such as a semiconductor chip. A print board module including the printed-wiring board mounted with the circuit element and an electronic device, such as a PC, having such a print board module exhibit similar operations.
The plurality of pads may include a first pad to be mounted with the circuit element, and unobservable after the circuit element is mounted thereto, and a second pad not to be mounted with the circuit element, the identifier being determined based on a position of the second pad. Use of the position of the second pad that is not to be mounted with the circuit element to indicate the identifier does not require the circuit element to be removed from the printed-wiring board but enables the printed-wiring board to be identified with the circuit element mounted onto the printed-wiring board. This second pad may be called a dummy pad.
The plurality of pads include a pad having a first shape, and a pad being located at a specific position and having a second shape different from the first shape, and wherein the identifier is determined based on the specific position and/or the second shape. This printed-wiring board changes pad""s shape and are identifiable based on the specific position or the second shape. The position of the pad is, for example, a coordinate position from a preset origin, while the shape of the pad is, for example, a circle. Here, xe2x80x9cbased onxe2x80x9d includes derivatives of the position and/or the second shape, such as a position determined by the specific position, e.g., a position next to or above the specific position. The first and second shapes are, for example, a circle, a rectangle, a pentagon, a hexagon, an octagon, and a cross.
At least one of the plurality of pads are provided with and protected by a protective mask that has an opening smaller than a contour of at least one of the plurality of pads, through which opening the circuit element is electrically connectible to at least one of the plurality of pads. This printed-wiring board sets the second shape to the pad provided with the protective mask, such as a SMD (Solder Mask Definition) pad, and maintains the stable electric connection between the circuit element and the pad unless a shape of the opening is changed in the protective mask on the pad. This aspect of the present invention is preferable, for example, to a change of a shape of a pad that has no protective mask, such as an NSMD or NON-Solder Mask Definition pad, since such a pad is expected to use its entire surface for electric connection with the circuit element and has already been designed to be optimal to the electric connection.
The plurality of pads may include a pad having a first shape, and a plurality of pads forming a specific design and each having a second shape different from the first shape, and wherein the identifier is determined based on the design. This printed-wiring board expresses the identifier using the design, e.g., a shape and/or position of the design expressed by the plural pads, and/or the second shape, instead of using alphabets and numerals put on the non-conductive part in the conventional printed-wiring board. The design may be provided in the above dummy and SMD pads.
The identifier may identify at least one piece of identification information including a drawing number that instructs a design drawing of the printed-wiring board, an inboard position number that instructs a position in a board at which the printed-wiring board is taken out, and a country of production, manufacturer, size, version, the number of layers, name, and date of manufacture of the printed-wiring board.
A contour of at least one of the plurality of pads is preferably larger than an area in which the circuit element contacts another pad, so as to maintain a good electric connection between the pad and the circuit element.
A method of another aspect according to the present invention for identifying a printed-wiring board including a plurality of pads adapted to assist in an electrical connection between a wiring pattern and an electronic element mounted onto the printed-wiring board includes the steps of selecting a specific position among the plurality of pads in the printed-wiring board, and setting the pad located at the specific position to a shape different from another pad at another position. This method also changes a shape of a pad that has been originally provided to the printed-wiring board to identify the printed-wiring board based on a position or shape of the pad.
The plurality of pads may include a first pad to be mounted with the circuit element and unobservable after the circuit element is mounted thereto, and a second pad not to be mounted with the circuit element, wherein the selecting step selects the specific position from the second pad. This method selects the second pad not to be mounted with the circuit element, such as a dummy pad, which will be described later, and enables the printed-wiring board to be identified without removing the circuit element from the printed-wiring board, i.e., while the printed-wiring board is mounted with the circuit element.
The selecting step may select the specific position from a pad provided with and protected by a protective mask that has an opening smaller than a contour of the pad provided with the protective mask, through which opening the circuit element is electrically connectible to the pad located at the specific position. The above pad is, for example, a SMD (Solder Mask Definition) pad. This method has an advantage in that the circuit element and the pad are stably connected unless a shape of the opening is changed in the protective mask above the pad. This aspect of the present invention is preferable, for example, to a change of a shape of a pad that has no protective mask, such as an NSMD or NON-Solder Mask Definition pad, since such a pad is expected to use its entire surface for electric connection with the circuit element and has already been designed optimal to the electric connection.
A method of still another aspect according to the present invention for identifying a printed-wiring board including a plurality of pads adapted to assist in an electrical connection between a wiring pattern and an electronic element mounted onto the printed-wiring board, the plurality of pads including a pad having a first shape and a pad being located at a specific position and having a second shape different from the first shape includes the steps of obtaining information of the specific position or the second shape in the printed-wiring board, and identifying a management item for the printed-wiring board by referring to a table that has been prepared in advance and correlates the information with the management item. This method also exhibits operations similar to the above method. The information of the specific position or the second shape covers, as mentioned above, the specific position itself and a position determined by the specific position, such as a position next to the specific position.
As discussed above, the above identifying method may determine the identifier based on the design assigned to one or more different shaped pads. More specifically, the identifier in this case is determined by a shape and/or position of the design, and/or pad""s shape. The design may be provided in the above dummy and SMD pads.
A method according to the present invention for manufacturing an identifiable printed-wiring board including a plurality of pads adapted to assist in an electrical connection between a wiring pattern and an electronic element mounted onto the printed-wiring board includes the steps of setting a pad at a specific position in the plurality of pads to a specific shape different from another pad at another position so as to identify the printed-wiring board, and making the plurality of pads through an etching process. This method is for manufacturing the identifiable printed-wiring board based on the specific position or shape, and exhibits the aforementioned operations.
Other objects and further features of the present invention will become readily apparent from the following description of the embodiments with reference to accompanying drawings.